# Copyright 2020 Zhejiang Lab and Zhejiang University. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# =============================================================

from .base import Callback
from typing import Sequence

class LRSchedulerCallback(Callback):
    r""" LR scheduler callback
    """
    def __init__(self, schedulers=None):
        super(LRSchedulerCallback, self).__init__()
        if not isinstance(schedulers, Sequence):
            schedulers = ( schedulers, )
        self._schedulers = schedulers

    def __call__(self, trainer):
        if self._schedulers is None:
            return
        for sched in self._schedulers:
            sched.step()